Age resistor for rubber



Patented July 27, 1943 2,325,202 I AGERESISTOR FOR RUBBER Albert M.Clifford, Stow, Ohio, assignor to Wing- '3 Akron, Ohio, a corporationofv foot Corporation, Delaware 7 No Drawing. Application July 13, 1940,

This invention relates to the treatment of rubber and-more particularlyto theme inrubberof age'resistors formed by reacting a di(arylamino)methane and a diaryl amine inthe presence of anacid. Many compounds areknown which; when incorporated into rubber, will [prevent or retardnatural deterioration'of therubber due to the effects of oxygen, light,flexing, heat, etc, 7 According to the; present invention, anew class ofage resistors for rubber has been discovered, .the compounds of whichare highly effective 'forpretarding such deterioration. f If a primaryand amine is reactedwith formal dehyde, a number of products arepossible, dc

, pending upon the molecular proportions of the reactants, thetemperature, presence of acids, etc; If one mol of formaldehyde istreated withtwo mols of a primary aryl amine under such conditions as toefiect a condensation; with attendant splitting'out of water, thepredominant reaction involves a linkage of two molecules of the aminethrough a methylene groupaccordingfto thefoL lowing equation:

(1) 2RNH2+HCHO 1 Rr-NH-CH2NHR+HZO These aldehyde-amine derivatives maybe called di(arylamino) methanes. vThe simplest material of this type ismethylene dianilid, which has the structural formula and is obtained byreacting two mols of aniline with one mol of formaldehyde according tothe Serial'No. 346,188 soldiers; (mecc -s09) (2) oemnn-cnz-Nn ogmlioam-Nu l The preparation oftthe' age resistors of their;-

."Em a1"npl e 1 v. 1 One mol of methylene dianilidwas' prepared bymixing 186 grams z -mols) of aniline and B1 vention is illustrated. bythe followingjegramples.

Y gramsil mol) of 40% formaldehydeandiallowing'the mixture to remainwarm for ..l%"'liours; I Twohundr ed nineteen grams (1;m01);:.of phenylbetaenaphthylamine were then added with stir ring and the mixture waswarmed until'complete solutionwas effected." Eighty-threecc, (1 mol) ofconcentrated hydrochloric acid (51); gr; 1.18) were; then addedgradually and the migture was stirred and heated; at 190+l00s :Cjjfor 19hjours'; The reactionproduct was then'made'alkaline with sodium"hydroxide to lib'eratethe aniline from the aniline hydrochloride'formedin'the'reaction and was then subjected to steam distillae tion until allof the anilinejhad been'fremoved; v The resi due"was then washed withwater and dried and when so purified weighed SZefgrams, which wasequivalent to the theoreit icalyin'eld;-

.e E a p 2' "Zone-half mol'of methylene'dia'nilid was-prepared as inExample 1. "One "hundred thirty grams mol) of diphenyl-para-pheny lenediamine and. 41 cc.- 'mo l) of I concentrated hydrochloric acid were addedand the 1 mixture was stirred and warmed at 80--95 CL forf20 hours: Thecrude product was made 'alkaline with so 'diuin' hydroxide and theaniline was removedfby' accompanied by nuclear substitution of thediaryl steam distillation. The'residu'e was thenwashed several timeswith water and dried. The product weighed grams; H T Mab e i-"Ninety-'three g rams- (1 mol)" or 'n-iline and /2 rams (1/2:-'1I 101)of i0 %-for maldehyde weremixed and allowed to 'react 'for '15 minutesr:1; Ninety One-half mol of methylene dianilid was prea pared as inExample 1 and, to this, 1241/: grams of beta-naphtho-phenothiazine (/2mol) were added as a fine powder.

The mixture was stirred and heated to 70-90 C. for about :s h'ours toproduce a homogeneous solution and then 41 cc.

mol) of concentrated hydrochloric acid were added slowly, keeping thetemperature below- 90 C. by cooling. The reaction mixture was thenheated, with occasional stirring, at 92-94 Cffor hours. The crudeproduct was made alkaline withsodium hydroxide} was steam distilled toremov th aniline, and was then washed with water and Thus purified, itwas a dark yellow waxand weighed 200 grams.

Any other ditarylamino) methane may beused in placeofth'emethylenedianilid of the foregoexarnpl es. Such compounds may beprepared by substituting other aldehydes and primary aryl aminesfoiifprmaldehyde and aniline. For exam le. aceta deh de may be sed np aof formal eh de: Th nr maryar amin z loyed, in the case of phenylamines, should preferably have, a free position para to the amino groupbut, except for this limitation, almost any primar 'arylamine willproduce a di(ary l amino) nieth'anef Suitable amines includ in addit onto aniline, alphaenaphthylamine', e aa htha.

j nd heik and matures wee; In addition,,.these. ai'y an'i nes may.contain various neutral or basic. subsutuent's "such alkyl,aryLaralkyLalkoxy, arylox'y. amino andhyclrcxyl groups ".w'hich'areiiie'rt in the tar-ther reaction of the; qitarylaminoi metnanestoproduce the. de-

sired. age r ist rs and whichidol n'ot"exer tanjy detrimental effect onthe action of. the age re-. 7

sisters in; rubber. Substituted diCarYIamlhOI meme substitueuts. are.for the purposes a: the presentinvehtion. filleduiva, lents at the.diO-Iylaminol lmethailesan arejill: tended; tofbe, mver'ed. theclaims. j

' jsuchdigairyla ninpi methanes are reacte witn a he ilrsme" ren: 11 (1-ganic acid,'such"as hydrochloric acid. Hydrobromic acid may alsobe usedbut it has the dising'with'water, and thenwith hydrochloric acid dventaeq eme. ex n i e a l v -ir hle'rf w le s l uri i mett disadvantage thatit-causessulionationof; thearyl Thus, ltheusli, othe rens m ter-m ids bwe. yd ochlor a d is e se e s h m oy d-i -=te e wathlarrla ames n wh t el, up areh dmarboa mine ma e e r.- sl b ime i e s c as ,alkyl,

an. 'a alkrh. s tes... m amine. and

droxyl group mayalso bewemployedsinca-as noted above, such groups arsubstantially inert and do not adversely aifect the age resistors{oi-mam; fiuchasubstttntedramin s. t

pmmsestoi tbqimsenainmtmn, full-.eeuivelents e-the: dimmeatandaareintndqkmbe ered bytheeleims. lmad lti exe e m ander:

amines, such as the thiazines and oxazines may be employed. Theme ofsuch materials is illustrated in Example 4. In the case of phenylamines,the tendency is for the nuclear substitution to take place para to theamino group. In the case of alpha-naphthylamines and betanaphthylaminesthe tendency is for the substitution to take place in thebeta and alpha positions, respectively. These effects may be dependentupon lability of the hydrogens, or steric hindrai ce; in any event, theyarewenmwn among organic chemists; In view of these effects, it isdesirable to have at least one such position free, i. e., containinghydrogen rather than a substituent radical.

The di(arylamino) methane, the diarylamine and the acid may be used in awide range of proportions while'still obtaining the desired ageresistors. The three components may react in substantially equimolecularproportions, as shown in Equation 2 Also, it is possible for nuclearsubstitution to take place on each of the aryl groups of thediarylamine. In such case, more than one, mol of di(arylamino) methanemay be employed roe; each incl. of' diarylamine and the acid} should. beincreased .to an amount equivaent tothedfiarylaminol methane. When.either of the reactants is in excess of the amount of material whichwill react, the excess merelyv carries through the product as animpurity which can be removed if. desired. In some cases such removal'isnotnecessary andthe impureproduct cab; be used. directly as anageresistor.

temperature which will effect splittingof the di(a'rylamino)' methaneand .nuclear substitution of the diarylai'riine may be employed.Suitable temperatures; areapproximately. 65- C. to C. The. pressure isnot. critical and at: mospheric pressure is convenient andsatisfac-.The.' agefres' tors of the invention, when. em? ployed withmercaptothiazole type accelerators, exert a slightactivati'ng influenceon these accelerators so. that the amount. of accelerator ordinarilyemployed. canfb'e'somewhat. reduced If iti's desired to lessen...thisactivating influence, the age resistors of the inventionamay bra-furtherreacted with a phenolic compound as illustrated by the followingexample. 7

One hundred five grams "cfthe product of Ex ample2 and m grams ofsbetanaphtholiwere heated in the presence of one gram of iodine at atemperature of 200-230 C; At the'end of 8 hours the evolution of waterhad ceased and the crude productthus obtained was washed with dilutesodium hydroxide followed by washand was; finally steam distilled. Thusit weighed grams, V

liex me hrle e etraa Stearic aeid; k5 Antioxidant The following testdata were obtained using the products of Examples 1-5.

What I claim is: a

1. The method of treating rubberwhich Icoml Before ageing After ageingCine in Mod.,kgs./ Mod.,kg./ Percent $125; IF Tens. in Elg. in Tens. inElg. in m per cent kgsJcm. per cent kgsJcm. percent 3 165 785 26 99 v162 720 37 149 .43 100 166 725 36 141 164 685 46 .44 142 815 21 73 123760 132 675 46 148 700 103 159 730 so. 135 165 695 1 96 860 14 32 111800 is so I 140 800 13 55 140 780 89 110 148 800 21 81 172 760 32 122.01

120 765 v23 so 112 70c 113 143 730 31 120 130 675 as .09 1 80 The actionof the age resistors inimparting 25 prises vuloanizing it in thepresence of the prod- I ood flex life to rubber was tested in a stock ofthe following composition:

Parts by weight Smoked sheet 100.0 Zinc oxide 5 5.50 Carbon black 43.00Sulfur -1 2.75 Stearic acid 4.00 Pine tar I 5.70 MercaptobenzothiazoleAs indicated Antioxidant 1.00

Because of the activating eifect of the age resistors, the amount ofmercaptobenzothiazole employed in each case was adjusted tov give thebest cure in 70 minutes at 260 F. The results obtained on stocks curedfor '70 and 140 minutes respectively at260 F. expressed in percentage ofthe flex life of a control in which the age resistor was phenyl beta notobtained by'reacting; at a temperature" of about 65 to 100 C.,-'adi.(ary1amino) methane and a diarylamine in the presence of hydro?chloric acid.

2.-The method of treating rubber which comprises yulcanizing'it in thepresence of the prod uct obtairiedqloyreacting, at a temperature ofabout 65100 C., a di(arylamino)' methaneand t hydrochloric acid.

a diarylamine in ganic acid.

3. The method of treating rubber which com prises vulcaniz'ing it'in thepresence of the prodnot obtained by reacting, at a temperatureof,about'65-100" C., methylene dianilid and a di arylamine in' the presenceof hydrochloric acid.

4. The method of treating rubber Which conp. prises vulcanizing it inthe presence of the prodnot obtained by reacting, at a temperature ofabout C.,,methylene dianilid and phenyl the, presence of hydro- I.

beta naphthylamine in. chloric acid.

5. The method of treating rubber which com prises vulcanizing it in thepresence ofv theprod not obtained by reacting, at a temperature of.about 65-100 C., methylene dianilidand di-' phenyl-p-phenylene diaminein the presence of the presence of a strong inor- ALBERT M. CLIFFORD. v

